The present invention relates to a tub grinder in which the rotational speed of the tub is slaved to the rotational speed of the hammermill, and in particular, to use of a control mechanism with such a tub grinder which substantially dampens or slows the rotational acceleration of the tub in relationship to the hammermill, but allows the tub to decelerate rapidly in direct relation to the deceleration of the hammermill.
The prior art discloses a number of tub grinders among which are included U.S. Pat. No. 3,912,175 to Anderson, U.S. Pat. No. 3,966,128 to Anderson et al and U.S. Pat. No. 4,033,515 to Barcell et al. The basic concept for the tub grinder involves the placement of forage in a rotating tub which urges the forage to pass over an opening in a floor beneath the tub. A hammermill extends through the opening, terminating slightly above the floor, and rotates so as to grind the feed into small pieces, whereby livestock may feed more easily thereon and there is less wastage thereof. The hammermill is often driven by a power take-off from a farm vehicle, although some units have a self contained power source. When the tub rotates too fast and thus overloads the hammermill, thereby slowing same, efficiency is lost and actual damage may be done to the machinery of the hammermill and/or farm vehicle supplying the power. Thus, a governor is normally included in such tub grinders, so as to slave the rotation of the tub to the speed of the hammermill, such that rotation of the tub is decelerated whenever the hammermill becomes chocked or is slowed and accelerated whenever the hammermill is able to accept more forage.
The major problem associated with the above described conventional tub grinders is that the rotation of the tub often begins to oscillate between acceleration and deceleration rather than maintaining a somewhat optimum constant speed and such oscillations often gain in amplitude with each cycle. The tub grinders, while designed to be sturdy in construction, are not able to withstand such oscillations over a long period of time and thus fail rapidly. Even if the tub grinder is able to withstand the oscillations, the power take-off system of the farm implement may be damaged. Thus it is desired to somehow effect a more stable rotational speed in the tub, yet leaving the tub to still be slaved to the hammermill, so that the hammermill will not be overloaded. The prior art reveals a number of indirect devices such as baffles, plates, and crossover bars to induce forage to feed more evenly to the hammermill. These devices have had varying degrees of effectiveness. However, a more direct mechanism has been needed which dampens the oscillations to prevent overload and seeks efficient operating conditions.
In addition, a dampening mechanism is desired which will not hamper deceleration or the complete stoppage of the tub, such that if the hammermill does become overloaded or choked with forage, the tub rotation will cease quickly before serious damage is done to the hammermill and/or power source. Thus, preferably a dampening system allows immediate proportional deceleration of the tub rotation with respect to the hammermill rotation but substantially delays the acceleration of the rotation of the tub or will accelerate the tub at a rate less than in proportion to the acceleration or speed of the hammermill.